Generally, a cathode ray tube (CRT) has been one of widely used display devices. The CRT is mainly used for television monitors, in measuring instruments, information terminal equipment, etc. However, with the demand for miniaturization and lightweight design of electronic products, the CRT is problematic due to the weight and size of the products.
Therefore, to replace the above cathode ray tube, various flat panel display (FPD) devices such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission display (FED) devices and electroluminescence display (ELD) devices have been researched and developed. The FPD devices thin, lightweight and have low power consumption, compared with CRTs.
Among these display devices, the organic electroluminescence display is a display device that electrically excites fluorescent organic compounds to emit light, which can display an image by voltage-driving or current-driving an array of M×N organic light emitting pixels.
The organic electroluminescence display can display colors close to natural colors since it can express visible light such as blue. The organic electroluminescence display has a high brightness and low power consumption. Moreover, the organic electroluminescence display does not have a limited viewing angle and is stable under low temperature conditions, unlike a liquid crystal display device provided with a liquid crystal layer. In addition, because the organic electroluminescence display is self luminescent, it is suitable for an ultra-thin type display device, and its production cost can be lowered because it has a simple manufacturing process. The organic electroluminescence display is also suitable for displaying moving images device as the response time is a few microseconds (μs).
As an organic electroluminescence display, an active matrix type in which a plurality of pixels is arranged in a matrix form and image information is selectively supplied to each pixel through a switching element, such as a thin film transistor, has been widely applied.
FIG. 1 is an exemplary view showing a general active matrix organic electroluminescence display.
Referring to FIG. 1, the organic electroluminescence display includes a plurality of gate lines GL1 to GLm and data lines DL1 to DLn arranged on a substrate 1 in longitudinal and transverse directions, a plurality of pixels P1 provided on areas defined by the gate lines GL1 to GLm and the data lines DL1 to DLn crossing each other, a data driving unit 30 for supplying an image signal to the pixels P1 via the data lines DL1 to DLn, and a gate driving unit 20 for applying scanning signals to the pixels P1 via the gate lines GL1 to GLm.
The gate driving unit 20 applies scanning signals to the gate lines GL1 to GLm in sequence. Switching elements electrically connected to the gate lines GL1 to GLm to which the scanning signals are applied are conductive, and the data driving unit 30 applies image signals to the data lines DL1 to DLn, thereby applying the image signals to the pixels P1 via the conductive switching elements. Each pixel P1 generates light by an organic electroluminescence device (not shown) according to the voltage level of input image signals.
With recent improvement of the resolution of organic electroluminescence displays, it is possible to realize sharper images. However, this is restricted by a limited space of the substrate 1 because a great deal of data lines DL1 to DLn has to be formed on the substrate 1 in order to realize a high resolution. Therefore, intervals between the lines to be formed get narrower and thus, signal interference occurs between the lines, thereby resulting in degradation of image quality.
To solve such problem, a block driving method was employed, which can supply image signals to the entire pixels P1 by limiting the number of data lines DL1 to DLn to be formed on the substrate 1 and repeatedly using the formed data lines DL1 to DLN many times.
The aforementioned block driving method will now be described in detail with reference to the accompanying drawings.
FIG. 2 is an exemplary view showing a block-driven organic electroluminescence display.
Referring to FIG. 2, the organic electroluminescence display includes a plurality of gate lines GL11 and GL12 and data lines DL11 to DL1n arranged on a substrate at regular intervals, a plurality of signal lines 140 arranged on the substrate at regular intervals, crossing the gate lines GL11 and GL12, and connected to the data lines DL11 to DL12, a plurality of pixels P11 provided on areas defined by the signal lines 140 and the gate lines GL11 and GL12 crossing each other, and a plurality of switching blocks BL1 to BLk provided on the signal lines 140, respectively, and controlling image signals delivered to the pixels P11 via the data lines DL11 to DL1n. 
In the block driving method, the display device is driven by dividing the entire screen of the display device and supplying image signals to pixels P11 via each switching block BL1 to BLk. In FIG. 2, a multiplicity of switching blocks BL1 to BLk for dividing the entire screen perpendicularly is shown.
In the drawing, the data lines DL11 to DL1n are formed on the substrate in a horizontal direction which is the same as the direction of the gate lines GL11 and GL12. As above, the number of the data lines DL11 to DL1n formed on the substrate is consistent with the number of the signal lines 140 connected to each of the switching block BL1 to BLk. That is, only the number of the data lines DL11 to DL1n required for simultaneously transmitting an image signal to one switching block BL1 to BLk are formed. The switching blocks BL1 to BLk consist of a plurality of switches 111, and each switch 111 is electrically connected to the data lines DL11 to DL1n, respectively, via the signal lines 140.
The signal lines 140 and the gate lines GL11 and GL12 define a plurality of pixels P11 by crossing each other perpendicularly. The pixels P11 are arranged in a matrix on the substrate.
Each of the pixels P11 is provided with a device, such as a thin film transistor. This thin film transistor is electrically connected to the gate lines GL11 and GL12 and the signal lines 140.
One side of the signal lines 140 is electrically connected to one of the plurality of data lines DL11 to DL1n, while the other side thereof is electrically connected to one of the plurality of pixels P11. Each of the signal lines is provided with a switch 111 for conducting or blocking signals from the pixels P11 to the data lines DL11 to DL1n. 
In the thus constructed organic electroluminescence display, when scanning signals are applied to the gate lines GL11 and GL12, the thin film transistors connected to the corresponding gate lines GL11 and GL12 are turned on. An image signal applied to the data lines DL11 to DL1n during the turn-on period is applied to the pixels P11 in units of the switching blocks BL1 to BLk via the signal lines 140.
Because the plurality of data lines DL11 to DL1n are commonly connected to each switching block BL1, they do not need to be formed so as to correspond to the entire substrate and the number of data lines to be formed can be reduced.
FIG. 3 is an exemplary view showing the timing of signals upon block driving.
Firstly, though a low voltage driving or high voltage driving may be selected according to the type of thin film transistors provided in the pixels, a description thereof will be based on a p-type thin film transistor that is turned on at a low voltage level.
As shown in FIG. 3, a scanning signal GS11 supplied from a gate driving unit (not shown) to gate lines is changed from a high voltage level to a low voltage level, block driving signals BE11 to BE1k are sequentially applied to switching blocks in a low voltage level section.
When each block driving signal BE11 to BE1k is sequentially applied to each switching block corresponding to the entire panel in a first horizontal period during which the scanning signal GS11 maintains a low potential level, every switching block is conductive once and image signals are supplied to corresponding pixels via the connected switching blocks. In this manner, the pixels connected to the gate lines, to which the scanning signal GS11 is applied in the first horizontal period, are all supplied with the image signals. As shown therein, the first block driving signal BE11 to the K-th block driving signal BE1k are applied at a low potential level pulse.
Generally, a resistance component, a capacitor component and a conductance component exist on a line to which an electric signal is delivered. Likewise, a capacitor component exists on the aforementioned signal lines, and thus the problem of signal distortion may occur.
In a case where block driving signals BE11 to BE1k are sequentially supplied to the switching blocks during the first horizontal period, the signal lines electrically connected to each switch of the switching blocks switched on are supplied with image signals from the data lines. Consequently, these image signals are supplied to the pixels. Since the scanning signal GS11 sequentially applied to the gate lines is generated at regular intervals so that each signal does not overlap with each other, it is not until a predetermined (dummy) time passes after the scanning signal GS11 becomes a low voltage level that the next scanning signal GS11 is generated.
However, a portion of the electric charge corresponding to the image signals remain on the signal lines even during this dummy time, and may affect the driving of the pixels. Moreover, as shown therein, as each switching block is conductive during the previous horizontal period, the image signals applied to the signal lines cannot be supplied with new image signal until each switching block is conductive in the next horizontal period. For example, the image signals applied in the previous horizontal period still remain on the signal lines during a dummy time A from the falling edge of the scanning signal GS11 to the first block driving signal BE11, a dummy time B from the falling edge of the scanning signal GS11 to the second block driving signal BE12, and a dummy time C from the falling edge of the scanning signal GS11 to the k-the block driving signal BE1k. Therefore, the image signals corresponding to the previous horizontal period may be supplied to the organic electroluminescence device of the pixels during the dummy times A, B and C of the next horizontal period. The above organic electroluminescence device may generate undesired light emission by maintaining components of the image signals applied during the short dummy times A, B and C because it has a fast reaction speed. This problem may not be serious in a liquid crystal display using liquid crystal with relatively low reaction speed, but may lead to picture quality degradation in the organic electroluminescence device. Especially, in a case where white images with a high brightness are displayed in the pixels in the previous horizontal period and black images with a low brightness are displayed in the same pixels in the next horizontal period, the light emission of the luminescence device caused by the remaining components of the image signals will degrade the picture quality greatly.